http://diversant.h1.ru/guns/granatomet/rpg1.html
machine translator:
In 1944 on Research range mortars arms of the Main artillery management have begun works on creation manual anti-tank grenade-launcher a complex as a part of grenade cup discharge LPG-44 and cumulative grenade PG-70 (the head of works - the leading designer of range G.P.Lominsky).
70-mm HEAT the cumulative grenade was charged with gun grenade cup discharge parts. For a throwing charge of a grenade the smoky gun gunpowder placed in a tube pomegranates was used. Grenade stabilisation in flight was carried out by means of the rigid stabilizer.
The grenade cup discharge represented jet system of reusable application. It had a smooth trunk in length of calibre of 1000 mm of 30 mm. On a trunk the cock of type and an aim lath fastened the with great dispatch-trigger mechanism (front sights on a grenade cup discharge were not. Since the aiming was made through a cut of a sight and on the top edge of a grenade). On a grenade cup discharge trunk wooden thermoprotective overlays fastened.
In 1944-45 have been conducted range of test of the grenade cup discharge which has received after that the official name "Manual anti-tank grenade cup discharge RPG-1", and a grenade - PG-1. Preparation of a batch production and manufacturing of experimental batches of grenade cup discharges and grenades have begun. Carrying out of large-scale tests and complex acceptance was planned for arms. However the considerable time spent for completion of shots to a grenade cup discharge (it has been connected with unsatisfactory action of a grenade because of imperfection of its detonator, and lacks of a powder charge on stability of burning at various temperatures in the summer and in the winter), became the reason of an obsolescence of a complex. Works on RPG-1 proceeded till 1948, but to finish it it was not possible, and on arms it has not been accepted.